Buoyancy body

ABSTRACT

A buoyancy body intended to be used in motorboats and sailing boats consists of a hermetically sealed flexible envelope containing a multiplicity of relatively small pieces of expanded plastic. The pressure within the envelope is slightly reduced so that the atmospheric pressure compacts the contents of the envelope.

United States Patent [191 Svanholm May 6,1975

[ BUOYANCY BODY [22] Filed: June 12, 1973 [21] Appl. No.: 369,145

[30] Foreign Application Priority Data June 15, 1972 Sweden 7862/72 [52]US. Cl 114/69; 9/8 R; 114/50 [51] Int. Cl B63b 43/00 [58] Field ofSearch 9/8 R, 8 P, 314, 344; 114/.5 F, 50, 69; 244/5 [56] ReferencesCited UNITED STATES PATENTS 1,089,617 3/1914 Adams ll4/.5 F 3,050,7508/1962 Harrison 9/8 R 3,378,864 4/1968 Comes 9/314 3,450,374 6/1969Moore 244/5 3,727,252 4/1973 Bauermeister 9/344 FOREIGN PATENTS ORAPPLICATIONS 734,640 8/1955 United Kingdom 114/.5 F

Primary ExaminerRobert J. Spar Assistant ExaminerDonald W. UnderwoodAttorney, Agent, or Firm-l-Iill, Gross, Simpson, Van Santen, Steadman,Chiara & Simpson [57] ABSTRACT A buoyancy body intended to be used inmotorboats and sailing boats consists of a hermetically sealed flexibleenvelope containing a multiplicity of relatively small pieces ofexpanded plastic. The pressure within the envelope is slightly reducedso that the atmospheric pressure compacts the contents of the envelope.

2 Claims, 2 Drawing Figures BUOYANCY BODY BACKGROUND OF THE INVENTIONThis invention relates to a buoyancy body and more particularly to abuoyancy body that is intended to be used for increasing the buoyancy ofboats, such as motorboats and sailing boats, so as to help keeping themafloat in case they should be filled with water.

It is known to increase the buoyancy of boats by filling empty spaces inthe hull with expanded plastic or by providing hermetically sealed airpockets. Both of these methods are fairly expensive and, besides, cannoteasily be used in the case of existing boats but are best suited for usein conjunction with the production of the boats.

In accordance with the invention there is provided a buoyancy bodycomprising a multiplicity of pieces of a buoyancy material having adensity substantially less than that of water and a hermetically sealedflexible envelope enclosing the pieces of buoyancy material.

The buoyancy body according to the invention may be produced in a singlesize or possibly a few sizes, e.g. one size having a buoyancy of onekilogram and one size having a buoyancy of 5 kilograms in water, meaninga volume of slightly more than 1 liter and 5 liters, respectively.Depending on the required or desired increase of the buoyancy of theboat, a smaller or larger number of buoyancy bodies are used. Since thebuoyancy bodies are relatively small, they can advantageously be placedwhere a small space is available that cannot otherwise be utilized.Thus, since almost every boat has several smaller or larger spaces whichare not normally used for any practical purpose but which can be filledwith the buoyancy bodies, the latter need not detract appreciably fromthe useful space.

The invention will be better understood from the following descriptionof an exemplary embodiment shown in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a buoyancybody according to the invention, a portion of the envelope being brokenaway;

FIG. 2 is a view in cross-section taken along line II-Il of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawing, there isshown a buoyancy body which comprises a multiplicity of balls 11 ofexpanded plastic, viz. expanded polystyrene, enclosed in a hermeticallysealed flexible envelope 12 made from a length of plastic tubing. Thesealing of the envelope has been effected by pinching and heat sealingthe ends 13 of the length of tubing after the balls 11 have beeninserted and a slightly reduced pressure has been produced within theenvelope. Conventional packaging machines can be used for massproduction of buoyancy bodies according to the invention.

Owing to the reduced pressure within the envelope, the atmosphericpressure acting on the exterior side of the body will slightly compactthe buoyancy material constituted by the mass of polystyrene ballswithout deforming the individual balls, which are rigid, that is, theyare capable of withstanding a pressure difference between the interiorand the exterior of the envelope of 0.1 atmosphere or more (assumingthat the envelope is infinitely flexible). Therefore, the body as awhole exhibits some degree of plasticity so that its shape can beadapted to the shape of the space where it is placed.

The numerical value of the slight vacuum or reduced pressure within theenvelope 12 is not very critical and should be chosen in dependence ofthe size of the balls 1 l and the envelope 12 and the thickness andflexibility of the film from which the envelope is made so that thedesired degree of compactness, plasticity and shape permanence isobtained. The best value is most easily found through experiments butgenerally the absolute pressure within the envelope should be below oneatmosphere, but not lower than 0.8 atmospheres, at temperatures withinthe envelope below 25C. A preferred lower limit is 0.9 atmospheres.

The film from which the envelope of the buoyancy body is made of coursehas to be of such thickness and quality as to prevent the surroundingair from penetrating it and destroying the reduced internal pressure. Inthe exemplary embodiment shown, the envelope 12 is made from a triplelaminate consisting of two outer layers of polyethylene and anintermediate layer of polyamide and having a thickness of about 0.1millimeter. This laminate is capable of conferring on the buoyancy bodythe necessary mechanical strength and resistance to attack from oils orfuels. It should be noted, however, that films or laminates of othermaterials and of a thickness up to 0.5 millimeters can be used. Apreferred thickness range is 0.05 to 0.2 millimeters.

Although polystyrene in ball form and having a density of about 30kilograms per cubic meter is presently believed to be the best buoyancymaterial, other materials may be used as long as they have a densitythat is sufficiently low; the density should be not more than 100kilograms and preferably less than 50 kilograms per cubic meter.Moreover, although a buoyancy material in ball form is advantageous inthat it simplifies the filling of the envelope and also can facilitatethe plastic shaping of the buoyancy body, the bouyancy material may bein the form of more or less irregular pieces, e.g. pieces obtained bydisintegration of larger pieces of scrap material. The size of the ballsor pieces is not very critical but the maximum linear cross-sectionaldimension of the largest balls or pieces preferably is not more than 15millimeters, and for best results percent (by number or more of theballs or pieces should have a maximum linear cross-sectional dimensionmuch less than 15 millimeters, preferably between 2 and 5 millimeters.

The drawing illustrates the approximate preferred proportions betweenthe length, width and thickness of the buoyancy body according to theinvention, the volume of the illustrated buoyancy body being slightlymore than one liter. The flat configuration permits the surfaces of aspace to be covered with one or more fairly smooth and coherent layersof buoyancy bodies which layer or layers will not only increase thebuoyancy of the boat but also form a heat and sound insulation.

What I claim is:

l. A buoyancy body comprising a multiplicity of individual pieces of asubstantially rigid buoyancy material having density substantially lessthan that of water and a hermetically sealed substantially flat andrectangular flexible envelope enclosing the pieces of buoyancy material,the absolute pressure within the envelope being lower than oneatmosphere at sea level, but higher than 0.8 atmosphere, at temperaturesbetween 0 and 25C.

2. Buoyancy body as claimed in claim I in which the maximum linearcross-sectional dimension of the individual pieces is 15 millimeters orless.

1. A buoyancy body comprising a multiplicity of individual pieces of asubstantially rigid buoyancy material having density substantially lessthan that of water and a hermetically sealed substantially flat andrectangular flexible envelope enclosing the pieces of buoyancy material,the absolute pressure within the envelope being lower than oneatmosphere at sea level, but higher than 0.8 atmosphere, at temperaturesbetween 0* and 25*C.
 2. Buoyancy body as claimed in claim 1 in which themaximum linear cross-sectional dimension of the individual pieces is 15millimeters or less.